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encoding/json: don't indirect pointers when decoding null

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The indirect method checked the type of the child when indirecting a
pointer. If the current value is a pointer and we are decoding null, we
can skip this entirely and return early, avoiding the whole descent.

Fixes #31776

Change-Id: Ib8b2a2357572c41f56fceac59b5a858980f3f65e
Reviewed-on: https://go-review.googlesource.com/c/go/+/174699
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
This commit is contained in:
Romain Baugue 2019-05-01 14:52:57 +02:00 committed by Daniel Martí
parent cdd2c265cc
commit b6ec56bc26
2 changed files with 14 additions and 3 deletions
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7
src/encoding/json/decode.go
View File

@ -416,8 +416,9 @@ func (d *decodeState) valueQuoted() interface{} {
// indirect walks down v allocating pointers as needed, // indirect walks down v allocating pointers as needed,
// until it gets to a non-pointer. // until it gets to a non-pointer.
// if it encounters an Unmarshaler, indirect stops and returns that. // If it encounters an Unmarshaler, indirect stops and returns that.
// if decodingNull is true, indirect stops at the last pointer so it can be set to nil. // If decodingNull is true, indirect stops at the first settable pointer so it
// can be set to nil.
func indirect(v reflect.Value, decodingNull bool) (Unmarshaler, encoding.TextUnmarshaler, reflect.Value) { func indirect(v reflect.Value, decodingNull bool) (Unmarshaler, encoding.TextUnmarshaler, reflect.Value) {
// Issue #24153 indicates that it is generally not a guaranteed property // Issue #24153 indicates that it is generally not a guaranteed property
// that you may round-trip a reflect.Value by calling Value.Addr().Elem() // that you may round-trip a reflect.Value by calling Value.Addr().Elem()
@ -456,7 +457,7 @@ func indirect(v reflect.Value, decodingNull bool) (Unmarshaler, encoding.TextUnm
break break
} }
if v.Elem().Kind() != reflect.Ptr && decodingNull && v.CanSet() { if decodingNull && v.CanSet() {
break break
} }

10
src/encoding/json/decode_test.go
View File

@ -401,6 +401,11 @@ type B struct {
B bool `json:",string"` B bool `json:",string"`
} }
type DoublePtr struct {
I **int
J **int
}
var unmarshalTests = []unmarshalTest{ var unmarshalTests = []unmarshalTest{
// basic types // basic types
{in: `true`, ptr: new(bool), out: true}, {in: `true`, ptr: new(bool), out: true},
@ -656,6 +661,11 @@ var unmarshalTests = []unmarshalTest{
err: fmt.Errorf("json: unknown field \"X\""), err: fmt.Errorf("json: unknown field \"X\""),
disallowUnknownFields: true, disallowUnknownFields: true,
}, },
{
in: `{"I": 0, "I": null, "J": null}`,
ptr: new(DoublePtr),
out: DoublePtr{I: nil, J: nil},
},
// invalid UTF-8 is coerced to valid UTF-8. // invalid UTF-8 is coerced to valid UTF-8.
{ {